Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$50.30	8.401%	$54.5257	$54.53	$54.55	$54.50
Purchase #2	$147.30	3.138%	$151.9223	$151.92	$151.90	$151.90
Purchase #3	$222.72	3.470%	$230.4484	$230.45	$230.45	$230.40
Purchase #4	$57.40	3.393%	$59.3476	$59.35	$59.35	$59.30
Purchase #5	$203.33	3.575%	$210.599	$210.60	$210.60	$210.60
Purchase #6	$211.28	5.369%	$222.6236	$222.62	$222.60	$222.60
Purchase #7	$193.80	5.275%	$204.023	$204.02	$204.00	$204.00
7 purchase totals =	$1,086.13		$1,133.4896	$1,133.49	$1,133.45	$1,133.30